Add note that credits are needed even with a claude subscription #5339

Job	Run time
build-and-check	2m 39s
test-common	40s
test-packages/internal	42s
test-integration-packages/agent-runtime	43s
test-packages/agent-runtime	54s
test-integration-packages/internal	42s
test-integration-packages/billing	45s
test-integration-common	42s
test-integration-.agents	48s
test-cli	1m 13s
test-sdk	45s
test-.agents	40s
test-web	51s
test-integration-sdk	41s
test-integration-cli	39s
test-packages/billing	45s
test-integration-web	38s
	14m 47s

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